Chemical formula for methane Methane Chemical formula for methane Methane is a colorless highly flammable gas that is less dense than air. The methane molecule consists of four hydrogen atoms covalently one carbon atom. The chemical formula for methane is CH4 which is the simplest hydrocarbon of the alkane series. The molar mass of methane is 16.043 g/mol Methane is a major component of natural gas and is also produced from by anaerobic bacteria in septic tanks and in the digestive systems of animals. Methane readily undergoes combustion producing carbon dioxide and water. Methane + oxygen ==> carbon dioxide + water + energy CH4 + 2O2 ==> CO2 + 2H2O + energy What is the chemical formula for methane? | Reference.com What is the chemical formula for methane? A: Quick Answer The chemical formula for methane is CH4. This is the simplest example of a class of compounds called hydrocarbons. Methane occurs in nature, formed from breaking down plant material, in the digestive process in animals and in fossil fuel deposits. Full Answer Methane, also called natural gas, forms from the bonding of four hydrogen atoms to a single carbon atom.

The hydrogen and carbon atoms share electrons to fill their outer energy levels, producing a more stable configuration for both hydrogen and carbon. Methane is a greenhouse gas. Greenhouse gases travel into the atmosphere, trapping the sun's heat on Earth like the glass on a greenhouse. The trapped heat causes global temperatures to rise slowly. Methane is one of the culprits leading to the phenomenon of global warming. methane | chemical compound | Britannica.com chemical compound biogas Methane, colourless odourless gas that occurs abundantly in nature and as a product of certain human activities. Methane is the simplest member of the paraffin series of hydrocarbons and is among the most potent of the greenhouse gases . Its chemical formula is CH4. Encyclopædia Britannica, Inc. Chemical properties of methane Methane is lighter than air , having a specific gravity of 0.554. It is only slightly soluble in water . It burns readily in air, forming carbon dioxide and water vapour; the flame is pale, slightly luminous, and very hot.

The boiling point of methane is −162 °C (−259.6 °F) and the melting point is −182.5 °C (−296.5 °F). Methane in general is very stable, but mixtures of methane and air, with the methane content between 5 and 14 percent by volume, are explosive. Explosions of such mixtures have been frequent in coal mines and collieries and have been the cause of many mine disasters. The tetrahedral structure of methane (CH4) is explained in the VSEPR … Encyclopædia Britannica, Inc. Sources of methane In nature, methane is produced by the anaerobic bacterial decomposition of vegetable matter under water (where it is sometimes called marsh gas or swamp gas). Wetlands are the major natural source of methane produced in this way. Other important natural sources of methane include termites (as a result of digestive processes), volcanoes , vents in the ocean floor, and methane hydrate deposits that occur along continental margins and beneath Antarctic ice and Arctic permafrost .

Methane also is the chief constituent of natural gas , which contains from 50 to 90 percent methane (depending on the source), and occurs as a component of firedamp (flammable gas) along coal seams. Learn about the emission of methane, a greenhouse gas, by trees in wetland ecosystems. © Open University (A Britannica Publishing Partner) The tetrahedral geometry of methane: (A) stick-and-ball model and (B) showing bond angles and … Encyclopædia Britannica, Inc. wood The production and combustion of natural gas and coal are the major anthropogenic (human-associated) sources of methane. Activities such as the extraction and processing of natural gas and the destructive distillation of bituminous coal in the manufacture of coal gas and coke-oven gas result in the release of significant amounts of methane into the atmosphere . Other human activities that are associated with methane production include biomass burning, livestock farming , and waste management (where bacteria produce methane as they decompose sludge in waste-treatment facilities and decaying matter in landfills). Uses of methane Methane is an important source of hydrogen and some organic chemicals.

Methane reacts with steam at high temperatures to yield carbon monoxide and hydrogen; the latter is used in the manufacture of ammonia for fertilizers and explosives . Other valuable chemicals derived from methane include methanol , chloroform , carbon tetrachloride , and nitromethane. The incomplete combustion of methane yields carbon black , which is widely used as a reinforcing agent in rubber used for automobile tires . Role as a greenhouse gas Methane that is produced and released into the atmosphere is taken up by methane sinks, which include soil and the process of methane oxidation in the troposphere (the lowest atmospheric region). Most methane produced naturally is offset by its uptake into natural sinks. Anthropogenic methane production, however, can cause methane concentrations to increase more quickly than they are offset by sinks. Increased concentrations of methane in the atmosphere contribute to the greenhouse effect , whereby greenhouse gases (particularly carbon dioxide , methane, and water vapour) absorb infrared radiation (net heat energy) and reradiate it back to Earth ’s surface, potentially trapping heat and producing substantial changes in climate . Increased atmospheric methane also adds to the greenhouse effect indirectly.

For example, in methane oxidation hydroxyl radicals (OH−) remove methane by reacting with it to form carbon dioxide and water vapour, and as concentrations of atmospheric methane increase, concentrations of hydroxyl radicals decrease, effectively prolonging the atmospheric lifetime of methane. Learn More in these related articles: in climate (meteorology) Multimedia: Balanced Equation | Chapter 6, Lesson 1 | Middle School Chemistry Middle School Chemistry Chapter 6, Lesson 1 Multimedia Methane and Oxygen React In the reaction, the the bonds in the methane and oxygen come apart, the atoms rearrange and then re-bond to form water and carbon dioxide. The little number written at the lower right after an atom (subscript) tells how many of that atom are in the molecule. The big number written in front of a molecule (coefficient) shows how many of that molecule there are. All the atoms in the products come from the atoms in the reactants. Combustion of Methane Combustion Combustion Interactive Chemistry Worksheets for Students Combustion is the burning of a fuel with the production of energy or heat Examples of combustion reactions 1. Cellular respiration Cellular respiration is the process whereby cells in our bodies obtain energy.

Glucose reacts with oxygen producing carbon dioxide and water with the release of energy. Glucose + oxygen 2. The Combustion of fossil fuels Fossil fuels are made up of hydrocarbons. Hydrocarbons are compounds that contain the elements hydrogen and carbon. Examples are methane, CH4, propane, C3H8, butane, C4H10 and octane, C8H18 Hydrocarbons readily burn or undergo combustion reactions. Combustion may be complete or incomplete. Complete combustion of fossil fuels results the production carbon dioxide and water. The incomplete combustion of fossil fuels results in the formation of carbon monoxide and soot (carbon). 1. Complete combustion of methane: Burns with a blue flame Methane + oxygen 2. Incomplete combustion of methane producing carbon monoxide Methane + oxygen 3. Incomplete combustion of methane producing soot Burns with a yellow flame Methane + oxygen CH4 + O2 C + 2H2O As the amount of oxygen is decreased from a ratio of 2 to 1.5 to 1 in the above three equations, the combustion products change from carbon dioxide to carbon monoxide to carbon or soot.

As the soot is heated in the flame it produces a yellow flame. In real life there is a mixture of carbon monoxide and soot from the incomplete combustion of hydrocarbons as well as unburnt hydrocarbons. Overview of Greenhouse Gases | Greenhouse Gas (GHG) Emissions | US EPA Overview of Greenhouse Gases Total Emissions in 2014 = 6,870 Million Metric Tons of CO2 equivalent . Larger image to save or print. Gases that trap heat in the atmosphere are called greenhouse gases. This section provides information on emissions and removals of the main greenhouse gases to and from the atmosphere. For more information on the science of climate change and other climate forcers, such as black carbon, please visit Climate Change Science . 6,870 million metric tons of CO2: What does that mean? An explanation of units: A million metric tons is equal to about 2.2 billion pounds, or 1 trillion grams. For comparison, a small car is likely to weigh a little more than 1 metric ton. Thus, a million metric tons is roughly the same mass as 1 million small cars! The U.S.

Inventory uses metric units for consistency and comparability with other countries. For reference, a metric ton is a little bit larger (about 10%) than a U.S. "short" ton. GHG emissions are often measured in carbon dioxide (CO2) equivalent. To convert emissions of a gas into CO2 equivalent, its emissions are multiplied by the gas's Global Warming Potential (GWP) . The GWP takes into account the fact that many gases are more effective at warming Earth than CO2, per unit mass. The GWP values appearing in the Emissions webpages reflect the values used in the U.S. Inventory, which are drawn from the IPCC’s Fourth Assessment Report (AR4). For further discussion of GWPs and an estimate of GHG emissions using updated GWPs, see Annex 6 of the U.S. Inventory and the IPCC's discussion on GWPs . Exit Carbon dioxide (CO2) : Carbon dioxide enters the atmosphere through burning fossil fuels (coal, natural gas, and oil), solid waste, trees and wood products, and also as a result of certain chemical reactions (e.g., manufacture of cement).

Carbon dioxide is removed from the atmosphere (or "sequestered") when it is absorbed by plants as part of the biological carbon cycle. Methane (CH4) : Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills. Nitrous oxide (N2O) : Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste. Fluorinated gases : Hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for stratospheric ozone-depleting substances (e.g., chlorofluorocarbons, hydrochlorofluorocarbons, and halons). These gases are typically emitted in smaller quantities, but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases ("High GWP gases").

Each gas's effect on climate change depends on three main factors: How much of these gases are in the atmosphere? Concentration, or abundance, is the amount of a particular gas in the air. Larger emissions of greenhouse gases lead to higher concentrations in the atmosphere. Greenhouse gas concentrations are measured in parts per million, parts per billion, and even parts per trillion. One part per million is equivalent to one drop of water diluted into about 13 gallons of liquid (roughly the fuel tank of a compact car). To learn more about the increasing concentrations of greenhouse gases in the atmosphere, visit the Causes of Climate Change and the Climate Change Indicators: Atmospheric Concentrations of Greenhouse Gases pages. How long do they stay in the atmosphere? Each of these gases can remain in the atmosphere for different amounts of time, ranging from a few years to thousands of years. All of these gases remain in the atmosphere long enough to become well mixed, meaning that the amount that is measured in the atmosphere is roughly the same all over the world, regardless of the source of the emissions. How strongly do they impact global temperatures?

Some gases are more effective than others at making the planet warmer and "thickening the Earth's blanket." For each greenhouse gas, a Global Warming Potential (GWP) has been calculated to reflect how long it remains in the atmosphere, on average, and how strongly it absorbs energy. Gases with a higher GWP absorb more energy, per pound, than gases with a lower GWP, and thus contribute more to warming Earth. Global Warming Potential (100-year): 1 Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities. In 2014, CO2 accounted for about 80.9% of all U.S. greenhouse gas emissions from human activities. Carbon dioxide is naturally present in the atmosphere as part of the Earth's carbon cycle (the natural circulation of carbon among the atmosphere, oceans, soil, plants, and animals). Human activities are altering the carbon cycle–both by adding more CO2 to the atmosphere and by influencing the ability of natural sinks, like forests, to remove CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.

1 Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2014 . Larger image to save or print. The main human activity that emits CO2 is the combustion of fossil fuels (coal, natural gas, and oil) for energy and transportation, although certain industrial processes and land-use changes also emit CO2. The main sources of CO2 emissions in the United States are described below. Electricity . Electricity is a significant source of energy in the United States and is used to power homes, business, and industry. The combustion of fossil fuels to generate electricity is the largest single source of CO2 emissions in the nation, accounting for about 37 percent of total U.S. CO2 emissions and 30 percent of total U.S. greenhouse gas emissions in 2014. The type of fossil fuel used to generate electricity will emit different amounts of CO2. To produce a given amount of electricity, burning coal will produce more CO2 than oil or natural gas. Transportation .

The combustion of fossil fuels such as gasoline and diesel to transport people and goods is the second largest source of CO2 emissions, accounting for about 31 percent of total U.S. CO2 emissions and 25 percent of total U.S. greenhouse gas emissions in 2014. This category includes transportation sources such as highway vehicles, air travel, marine transportation, and rail. Industry . Many industrial processes emit CO2 through fossil fuel combustion. Several processes also produce CO2 emissions through chemical reactions that do not involve combustion; for example, the production and consumption of mineral products such as cement, the production of metals such as iron and steel, and the production of chemicals. Fossil fuel combustion from various industrial processes accounted for about 15 percent of total U.S. CO2 emissions and 12 percent of total U.S. greenhouse gas emissions in 2014. Note that many industrial processes also use electricity and therefore indirectly cause the emissions from the electricity production. Carbon dioxide is constantly being exchanged among the atmosphere, ocean, and land surface as it is both produced and absorbed by many microorganisms, plants, and animals. However, emissions and removal of CO2 by these natural processes tend to balance.

Since the Industrial Revolution began around 1750, human activities have contributed substantially to climate change by adding CO2 and other heat-trapping gases to the atmosphere. In the United States, since 1990, the management of forests and non-agricultural land has acted as a net sink of CO2, which means that more CO2 is removed from the atmosphere, and stored in plants and trees, than is emitted. This sink offset about 11 percent of total emissions in 2014 and is discussed in more detail in the Land Use, Land-Use Change, and Forestry section. To find out more about the role of CO2 warming the atmosphere and its sources, visit the Causes of Climate Change page and the Climate Change Indicators page in the Science section. Emissions and Trends Carbon dioxide (CO2) emissions in the United States increased by about 9 percent between 1990 and 2014. Since the combustion of fossil fuel is the largest source of greenhouse gas emissions in the United States, changes in emissions from fossil fuel combustion have historically been the dominant factor affecting total U.S. emission trends.

Changes in CO2 emissions from fossil fuel combustion are influenced by many long-term and short-term factors, including population growth, economic growth, changing energy prices, new technologies, changing behavior, and seasonal temperatures. Between 1990 and 2014, the increase in CO2 emissions corresponded with increased energy use by an expanding economy and population, and an overall growth in emissions from electricity generation. Transportation emissions also contributed to the 9 percent increase, largely due to an increase in miles traveled by motor vehicles. Larger image to save or print. Reducing Carbon Dioxide Emissions The most effective way to reduce carbon dioxide (CO2) emissions is to reduce fossil fuel consumption. Many strategies for reducing CO2 emissions from energy are cross-cutting and apply to homes, businesses, industry, and transportation. EPA is taking common sense regulatory actions to reduce greenhouse gas emissions from our nation's largest sources, including power plants and motor vehicles. Examples of How Emissions Can be Reduced Energy Efficiency Improving the insulation of buildings, traveling in more fuel-efficient vehicles, and using more efficient electrical appliances are all ways to reduce energy consumption, and thus CO2 emissions. See EPA's ENERGY STAR® program for more information on energy-efficient appliances.

See EPA's and DOE's fueleconomy.gov site for more information on fuel-efficient vehicles. Learn about EPA's motor vehicle standards that improve vehicle efficiency and save drivers money. Energy Conservation Reducing personal energy use by turning off lights and electronics when not in use reduces electricity demand. Reducing distance traveled in vehicles reduces petroleum consumption. Both are ways to reduce energy CO2 emissions through conservation. Learn more about What You Can Do at Home , at School , in the Office , and on the Road to save energy and reduce your carbon footprint. Fuel Switching Producing more energy from renewable sources and using fuels with lower carbon contents are ways to reduce carbon emissions. Carbon Capture and Sequestration Carbon dioxide capture and sequestration is a set of technologies that can potentially greatly reduce CO2 emissions from new and existing coal- and gas-fired power plants, industrial processes, and other stationary sources of CO2. Learn more . * Carbon dioxide's lifetime is poorly defined because the gas is not destroyed over time, but instead moves among different parts of the ocean-atmosphere-land system.

Some of the excess carbon dioxide will be absorbed quickly (for example, by the ocean surface), but some will remain in the atmosphere for thousands of years, due in part to the very slow process by which carbon is transferred to ocean sediments. References Global Warming Potential (100-year): 25 Methane (CH4) is the second most prevalent greenhouse gas emitted in the United States from human activities. In 2014, CH4 accounted for about 11 percent of all U.S. greenhouse gas emissions from human activities. Methane is emitted by natural sources such as wetlands, as well as human activities such as leakage from natural gas systems and the raising of livestock. Natural processes in soil and chemical reactions in the atmosphere help remove CH4 from the atmosphere. Methane's lifetime in the atmosphere is much shorter than carbon dioxide (CO2), but CH4 is more efficient at trapping radiation than CO2. Pound for pound, the comparative impact of CH4 on climate change is more than 25 times greater than CO2 over a 100-year period. Globally, over 60 percent of total CH4 emissions come from human activities.

1 Methane is emitted from industry, agriculture, and waste management activities, described below. Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2014 . Larger image to save or print. Industry . Natural gas and petroleum systems are the largest source of CH4 emissions from industry in the United States. Methane is the primary component of natural gas. Some CH4 is emitted to the atmosphere during the production, processing, storage, transmission, and distribution of natural gas. Because gas is often found alongside petroleum, the production, refinement, transportation, and storage of crude oil is also a source of CH4 emissions. For more information, see the Inventory of U.S. Greenhouse Gas Emissions and Sinks sections on Natural Gas Systems and Petroleum Systems. Agriculture . Domestic livestock such as cattle, buffalo, sheep, goats, and camels produce large amounts of CH4 as part of their normal digestive process. Also, when animals' manure is stored or managed in lagoons or holding tanks, CH4 is produced. Because humans raise these animals for food, the emissions are considered human-related.

Globally, the Agriculture sector is the primary source of CH4 emissions. For more information, see the Inventory of U.S. Greenhouse Gas Emissions and Sinks Agriculture chapter. Waste from Homes and Businesses . Methane is generated in landfills as waste decomposes and in the treatment of wastewater. Landfills are the third largest source of CH4 emissions in the United States. For more information see the U.S. Inventory's Waste chapter. Methane is also emitted from a number of natural sources. Wetlands are the largest source, emitting CH4 from bacteria that decompose organic materials in the absence of oxygen. Smaller sources include termites, oceans, sediments, volcanoes, and wildfires. To find out more about the role of CH4 in warming the atmosphere, and its sources, visit the Causes of Climate Change page and the Climate Change Indicators page in the Science section. Emissions and Trends Methane (CH4) emissions in the United States decreased by 6 percent between 1990 and 2014. During this time period, emissions increased from sources associated with agricultural activities, while emissions decreased from sources associated with the exploration and production of natural gas and petroleum products.

Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2014 . These estimates use a global warming potential for methane of 25, based on reporting requirements under the United Nations Framework Convention on Climate Change. Larger image to save or print. Reducing Methane Emissions There are a number of ways to reduce methane (CH4) emissions. Some examples are discussed below. EPA has a series of voluntary programs for reducing CH4 emissions, and is supporting the president's Strategy to Reduce Methane Emissions (15 pp, 1.9 M, About PDF ). EPA also supports the Global Methane Initiative Exit , an international partnership encouraging global methane reduction strategies. Examples of Reduction Opportunities for Methane Emissions Source How Emissions Can be Reduced Industry Upgrading the equipment used to produce, store, and transport oil and gas can reduce many of the leaks that contribute to CH4 emissions. Methane from coal mines can also be captured and used for energy. Learn more about the EPA's Natural Gas STAR Program and Coalbed Methane Outreach Program .

Agriculture Methane can be reduced and captured by altering manure management strategies at livestock operations or animal feeding practices. Learn more about these strategies and EPA's AgSTAR Program . Waste from Homes and Businesses Because CH4 emissions from landfill gas are a major source of CH4 emissions in the United States, emission controls that capture landfill CH4 are an effective reduction strategy. Learn more about these opportunities and the EPA's Landfill Methane Outreach Program . References Global Warming Potential (100-year): 298 In 2014, nitrous oxide (N2O) accounted for about 6 percent of all U.S. greenhouse gas emissions from human activities. Nitrous oxide is naturally present in the atmosphere as part of the Earth's nitrogen cycle, and has a variety of natural sources. However, human activities such as agriculture, fossil fuel combustion, wastewater management, and industrial processes are increasing the amount of N2O in the atmosphere. Nitrous oxide molecules stay in the atmosphere for an average of 114 years before being removed by a sink or destroyed through chemical reactions. The impact of 1 pound of N2O on warming the atmosphere is almost 300 times that of 1 pound of carbon dioxide.

Globally, about 40 percent of total N2O emissions come from human activities. 1 Nitrous oxide is emitted from agriculture, transportation, and industry activities, described below. Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2014 . Larger image to save or print. Agriculture . Nitrous oxide is emitted when people add nitrogen to the soil through the use of synthetic fertilizers. Agricultural soil management is the largest source of N2O emissions in the United States, accounting for about 79 percent of total U.S. N2O emissions in 2014. Nitrous oxide is also emitted during the breakdown of nitrogen in livestock manure and urine, which contributed to 4 percent of N2O emissions in 2014. Transportation . Nitrous oxide is emitted when transportation fuels are burned. Motor vehicles, including passenger cars and trucks, are the primary source of N2O emissions from transportation. The amount of N2O emitted from transportation depends on the type of fuel and vehicle technology, maintenance, and operating practices. Industry .

Nitrous oxide is generated as a byproduct during the production of nitric acid, which is used to make synthetic commercial fertilizer, and in the production of adipic acid, which is used to make fibers, like nylon, and other synthetic products. Nitrous oxide emissions occur naturally through many sources associated with the nitrogen cycle, which is the natural circulation of nitrogen among the atmosphere, plants, animals, and microorganisms that live in soil and water. Nitrogen takes on a variety of chemical forms throughout the nitrogen cycle, including N2O. Natural emissions of N2O are mainly from bacteria breaking down nitrogen in soils and the oceans. Nitrous oxide is removed from the atmosphere when it is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions. To find out more about the role of N2O in warming the atmosphere and its sources, visit the Causes of Climate Change page and the Climate Change Indicators page in the Science section. Emissions and Trends Nitrous oxide (N2O) emissions in the United States have decreased by 1 percent between 1990 and 2014. This decrease in emissions is due in part to a decrease in emissions from mobile combustion resulting from emission control standards for on-road vehicles.

Nitrous oxide emissions from agricultural soils have varied during this period and were about 5 percent higher in 2014 than in 1990. Going forward, N2O emissions are projected to increase by 5 percent between 2005 and 2020, driven largely by increases in emissions from agricultural activities. 2 There are a number of ways to reduce emissions of nitrous oxide (N2O), discussed below. Examples of Reduction Opportunities for Nitrous Oxide Emissions Emissions Source Examples of How Emissions Can be Reduced Agriculture The application of fertilizers accounts for the majority of N2O emissions. Emissions can be reduced by reducing nitrogen-based fertilizer applications and applying fertilizers more efficiently, 3 as well as following better manure management practices. Transportation Nitrous oxide is a byproduct of fuel combustion, so reducing mobile fuel consumption in motor vehicles can reduce transportation emissions. Additionally, the introduction of pollution control technologies, such as catalytic converters to reduce exhaust pollutants from passenger cars, can also reduce emissions of N2O. Industry Nitrous oxide is generally emitted from industry through fossil fuel combustion, so technological upgrades and fuel switching are effective ways to reduce industry emissions of N2O.

Production of adipic acid results in N2O emissions that can be reduced through technological upgrades. References NF3: 17,200 SF6: 22,800 Unlike many other greenhouse gases, fluorinated gases have no natural sources and only come from human-related activities. They are emitted through a variety of industrial processes such as aluminum and semiconductor manufacturing. Many fluorinated gases have very high global warming potentials (GWPs) relative to other greenhouse gases, so small atmospheric concentrations can have large effects on global temperatures. They can also have long atmospheric lifetimes—in some cases, lasting thousands of years. Like other long-lived greenhouse gases, fluorinated gases are well-mixed in the atmosphere, spreading around the world after they are emitted. Fluorinated gases are removed from the atmosphere only when they are destroyed by sunlight in the far upper atmosphere. In general, fluorinated gases are the most potent and longest lasting type of greenhouse gases emitted by human activities. There are four main categories of fluorinated gases—hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3).

The largest sources of fluorinated gas emissions are described below. Larger image to save or print. Substitution for Ozone-Depleting Substances. Hydrofluorocarbons are used as refrigerants, aerosol propellants, solvents, and fire retardants. The major emissions source of these compounds is their use as refrigerants—for example, in air conditioning systems in both vehicles and buildings. These chemicals were developed as a replacement for chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) because they do not deplete the stratospheric ozone layer. Chlorofluorocarbons and HCFCs are being phased out under an international agreement, called the Montreal Protocol. Unfortunately, HFCs are potent greenhouse gases with long atmospheric lifetimes and high GWPs, and they are released into the atmosphere through leaks, servicing, and disposal of equipment in which they are used. Industry. Perfluorocarbons are compounds produced as a byproduct of various industrial processes associated with aluminum production and the manufacturing of semiconductors. Like HFCs, PFCs generally have long atmospheric lifetimes and high GWPs.

Sulfur hexafluoride is used in magnesium processing and semiconductor manufacturing, as well as a tracer gas for leak detection. HFC-23 is produced as a byproduct of HCFC-22 production. Transmission and Distribution of Electricity. Sulfur hexafluoride is used in electrical transmission equipment, including circuit breakers. The GWP of SF6 is 22,800, making it the most potent greenhouse gas that the Intergovernmental Panel on Climate Change has evaluated. To find out more about the role of fluorinated gases in warming the atmosphere, and their sources, visit the Causes of Climate Change page and the Climate Change Indicators page in the Science section. Emissions and Trends Overall, fluorinated gas emissions in the United States have increased by about 77 percent between 1990 and 2014. This increase has been driven by a 258 percent increase in emissions of hydrofluorocarbons (HFCs) since 1990, as they have been widely used as a substitute for ozone-depleting substances.

Emissions of perfluorocarbons (PFCs) and sulfur hexafluoride (SF6) have actually declined during this time due to emission reduction efforts in the aluminum production industry (PFCs) and the electricity transmission and distribution industry (SF6). Going forward, HFC emissions are projected to grow by nearly 141 percent between 2005 and 2020 as demands for refrigeration continue to grow and as more ozone-depleting substances are replaced. During this same period, emissions of SF6 are expected to decline by over 25 percent, while emissions of PFCs are projected to remain flat. Since the emissions from HFCs are far greater than the emissions of the other gases on a carbon dioxide-equivalence basis, substantial growth in emissions of fluorinated gases is expected to continue. 1 Larger image to save or print. Reducing Fluorinated Gas Emissions Because most fluorinated gases have a very long atmospheric lifetime, it will take many years to see a noticeable decline in current concentrations. However, there are a number of ways to reduce emissions of fluorinated gases, described below.

Examples of Reduction Opportunities for Fluorinated Gases Emissions Source The PFC Reduction/Climate Partnership for the Semiconductor Industry Electricity Transmission and Distribution Sulfur hexafluoride is an extremely potent greenhouse gas that is used for several purposes when transmitting electricity through the power grid. EPA is working with industry to reduce emissions through the SF6 Emission Reduction Partnership for Electric Power Systems , which promotes leak detection and repair, use of recycling equipment, and employee training. Transportation Hydrofluorocarbons (HFCs) are released through the leakage of refrigerants used in vehicle air-conditioning systems. Leakage can be reduced through better system components, and through the use of alternative refrigerants with lower global warming potentials than those presently used. One important way the EPA is working to reduce HFC emissions is through its light-duty and heavy-duty vehicle standards . References (10 pp, 577 K, About PDF ). U.S. Department of State, Washington, DC, USA. Chemical of the Week -- Methane METHANE Methane is a colorless, odorless gas with a wide distribution in nature.

It is the principal component of natural gas, a mixture containing about 75% CH4, 15% ethane (C2H6), and 5% other hydrocarbons, such as propane (C3H8) and butane (C4H10). The "firedamp" of coal mines is chiefly methane. Anaerobic bacterial decomposition of plant and animal matter, such as occurs under water, produces marsh gas, which is also methane. At room temperature, methane is a gas less dense than air. It melts at 183°C and boils at 164°C. It is not very soluble in water. Methane is combustible, and mixtures of about 5 to 15 percent in air are explosive. Methane is not toxic when inhaled, but it can produce suffocation by reducing the concentration of oxygen inhaled. A trace amount of smelly organic sulfur compounds (tertiary-butyl mercaptan, (CH3)3CSH and dimethyl sulfide, CH3SCH3) is added to give commercial natural gas a detectable odor. This is done to make gas leaks readily detectible.

An undetected gas leak could result in an explosion or asphyxiation. (The attached scratch-and-sniff sheet from Madison Gas & Electric Company is for your use outside of class.) Methane is synthesized commercially by the distillation of bituminous coal and by heating a mixture of carbon and hydrogen. It can be produced in the laboratory by heating sodium acetate with sodium hydroxide and by the reaction of aluminum carbide (Al4C3) with water. In the chemical industry, methane is a raw material for the manufacture of methanol (CH3OH), formaldehyde (CH2O), nitromethane (CH3NO2), chloroform (CH3Cl), carbon tetrachloride (CCl4), and some freons (compounds containing carbon and fluorine, and perhaps chlorine and hydrogen). The reactions of methane with chlorine and fluorine are triggered by light. When exposed to bright visible light, mixtures of methane with chlorine or fluorine react explosively. The principal use of methane is as a fuel. The combustion of methane is highly exothermic.

CH4(g) + 2 O2(g) CO2(g) + 2 H2O(l) H = 891 kJ The energy released by the combustion of methane, in the form of natural gas, is used directly to heat homes and commercial buildings. It is also used in the generation of electric power. During the past decade natural gas accounted for about 1/5 of the total energy consumption worldwide, and about 1/3 in the United States. The cost of natural gas to Wisconsin consumers is regulated by the State Public Service Commission. Madison Gas Electric Company currently charges its residential consumers about $0.66 per 100 cubic feet. Natural gas occurs in reservoirs beneath the surface of the earth. It is often found in conjunction with petroleum deposits. Before it is distributed, natural gas usually undergoes some sort of processing. Usually, the heavier hydrocarbons (propane and butane) are removed and marketed separately. Non-hydrocarbon gases, such as hydrogen sulfide, must also be removed. The cleaned gas is then distributed throughout the country through thousands of miles of pipeline. Local utility companies add an odorant before delivering the gas to their customers.

Some methane is manufactured by the distillation of coal. Coal is a combustible rock formed from the remains of decayed vegetation. It is the only rock containing significant amounts of elemental carbon. The composition of coal varies between 60% and 95% carbon. Coal also contains hydrogen and oxygen, with small concentrations of nitrogen, chlorine, sulfur, and several metals. Coals are classified by the amount of volatile material they contain, that is, by how much of the mass is vaporized when the coal is heated to about 900°C in the absence of air. Coal that contains more than 15% volatile material is called bituminous coal. Substances released from bituminous coal when it is distilled, in addition to methane, include water, carbon dioxide, ammonia, benzene, toluene, naphthalene, and anthracene. In addition, the distillation also yields oils, tars, and sulfur-containing products. The non-volatile component of coal, which remains after distillation, is coke. Coke is almost pure carbon and is an excellent fuel. However, it may contain metals, such as arsenic and lead, that can be serious pollutants if the combustion products are released into the atmosphere.

Combustion of Fossil Fuels Teacher Sheet - Science NetLinks Science NetLinks Combustion of Fossil Fuels Teacher Sheet Part 1. The Combustion of Fossil Fuels. What do we mean that a hydrocarbon can go through combustion? What are we really doing to the hydrocarbon? We are burning it. Why do you think hydrocarbons make good fuels? They produce a lot of energy when combusted. Write the chemical reaction for the combustion of methane below. CH4 + 2O2 à CO2 +2H2O How does the combustion of methane compare to the combustion of other hydrocarbon fossil fuels, like coal and oil? The combustion of methane is cleaner, producing only water and carbon dioxide. The combustion of oil and coal is more complicated, and harmful air pollutants are produced. Par II. Energy of Combustion What is the general chemical formula for the combustion of fossil fuels, or any hydrocarbons? Fossil fuel plus oxygen produces carbon dioxide, water, and energy. Approximately what percentage of the world’s energy needs is fulfilled by the combustion of fossil fuels? Approximately 75%. Combustion produces energy. Where does all this energy come from?

Energy is stored in the chemical bonds that hold the carbon and hydrogen atoms together. When the atoms are rearranged, the bonds are broken, releasing energy. Based on the diagram for the energy used and produced in the combustion of methane, fill in the chart. Make sure to indicate whether the energy is positive or negative. Also indicate the units. Step What is the total net energy? -802 kJ Based on your calculations, is energy needed or produced to combust methane? How do you know this based on your calculation? Energy is produced in the combustion of methane. We know this because the total net energy is negative, indicating that energy is produced, not needed.What does the term “endothermic” mean? It means energy is required. In the steps above, which ones are endothermic? Steps 1 and 2. What does the term “exothermic” mean? It means energy or heat is produced. In the steps above, which ones are exothermic? Steps 3 and 4. Overall, is the combustion of methane endothermic or exothermic? It is exothermic. Part III. Combustion Energy of Ethane Different hydrocarbons produce different amounts of energy when combusted, or burned.

As we know from above, the combustion of methane produces 802 kJ of energy. How much energy is produced from the combustion of ethane? Use the bond energy chart found on the top of the online resource, Energy from Fossil Fuels ( ). What is the correct chemical reaction for the combustion of ethane? 2C2H6 + 7O2 à 4CO2 +6H2O Determine the bond energies in each step of the combustion of ethane. Two steps are provided for you as examples. Step 1:

Question: What is the chemical formula for methane?
Answer: CH4